digitalmars.D.dwt - Building DWT with GDC (.21) on Win32

Has anyone been able to get DWT to compile with GDC? I keep getting lots of
errors, particularly with OBJIDL.
"import\dwt\internal\ole\win32\OBJIDL.d:39: Error: identifier 'DWORD' is not
defined"
I thought the error may be cause by circular linking problems so I tried
compiling with "-fonly=import\dwt\all". This just results in the compiler
crashing.